- Stereoretentive Pd-catalysed Stille cross-coupling reactions of secondary alkyl azastannatranes and aryl halides
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The development of transition metal-catalysed cross-coupling reactions has greatly influenced the manner in which the synthesis of complex organic molecules is approached. A wide variety of methods are now available for the formation of C(sp2)-C(sp2) bonds, and more recent work has focused on the use of C(sp3) electrophiles and nucleophiles. The use of secondary and tertiary alkyl nucleophiles in cross-coupling reactions remains a challenge because of the propensity of these alkyl groups to isomerize under the reaction conditions. Here, we report the development of a general Pd-catalysed process for the stereoretentive cross-coupling of secondary alkyl azastannatrane nucleophiles with aryl chlorides, bromides, iodides and triflates. Coupling partners with a wide range of electronic characteristics are well tolerated. The reaction occurs with minimal isomerization of the secondary alkyltin nucleophile, and with retention of absolute configuration. This process constitutes the first general method to use secondary alkyltin reagents in cross-coupling reactions.
- Li, Ling,Wang, Chao-Yuan,Huang, Rongcai,Biscoe, Mark R.
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p. 607 - 612
(2013/07/26)
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- Nickel-catalyzed Negishi cross-coupling reactions of secondary alkylzinc halides and aryl iodides
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A general Ni-catalyzed process for the cross-coupling of secondary alkylzinc halides and aryl/heteroaryl iodides has been developed. This is the first process to overcome the isomerization and β-hydride elimination problems that are associated with the use of secondary nucleophiles, and that have limited the analogous Pd-catalyzed systems. The impact of salt additives was also investigated. It was found that the presence of LiBF4 dramatically improves both isomeric retention and yield for challenging substrates.(Figure Presented)
- Joshi-Pangu, Amruta,Ganesh, Madhu,Biscoe, Mark R.
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supporting information; experimental part
p. 1218 - 1221
(2011/04/27)
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- Process for the preparation of alkylated aromatic carboxylic acids and acyl halides
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The invention relates to a process for the preparation of polyalkylated aromatic carboxylic acids of formula I STR1 wherein R1, R2, R3, R4 and R5 are each independently of one another hydrogen, C1 -C20 alkyl, halogen or C5 -C8 cycloalkyl, with the proviso that at least two of the substituents R1, R2, R3, R4 or R5 are alkyl and/or cycloalkyl, by reacting corresponding aromatic hydrocarbons with carbon dioxide, which reaction is carried out observing special ratios of temperature and pressure. The invention furthermore relates to a one-pot process for the preparation of the corresponding acyl halides.
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